Conventionally, various kinds of particle dispersed resin compositions have been proposed of which resin characteristics are improved by mixing functional particulate powder with a resin. For example, there have been proposed flame retardant resin compositions with and in which flame retardant particulate powder is mixed and dispersed in a thermoplastic resin, such as high impact polystyrene or the like. Besides, there have been proposed various kinds of particle dispersed resin compositions, such as a heat-resistant anti-aging polyamide resin composition with and in which potassium iodide particulate powder or the like is mixed and dispersed (see Patent Document 1, for example), a low stress transparent resin composition with and in which silica based particulate powder is mixed and dispersed, a high strength resin composition with and in which particulate powder of a metal-containing oxide compound is mixed and dispersed, a magnetic resin composition, such as magnetic toner with and in which magnetic particulate powder is mixed and dispersed, and the like.
Such particulate powder will, however, cohere (secondarily) to form agglomerates in general. For this reason, even if such particulate powder is added to and mixed with a resin, the particulate powder, of which grain diameter is comparatively small, cannot be dispersed uniformly in the entire resin.
The cohesiveness of particulate powder correlates to the grain diameter of the particulate powder. Specifically, as the grain diameter of particulate powder is small, the cohesiveness thereof tends to increase. For example, particulate powder of which grain diameter is 1 μm or smaller exhibits especially high cohesiveness, and therefore, it is difficult to obtaining a resin composition with and in which such particulate powder having a diameter of 1 μn or smaller is mixed and dispersed uniformly.
In view of the foregoing problems, various kinds of methods for mixing and dispersing particulate powder uniformly with and in a resin have been proposed. For example, Patent Document 1 proposes a method of obtaining a particle dispersed resin composition in which a fluid dispersion obtained by dissolving or dispersing a solid additive (particulate powder) in a solvent is added to a thermoplastic resin in a melted state, the resultant resin is kneaded, and then, the solvent is volatilized. Patent Document 1 discloses that according to this method, secondary cohesion of the particulate powder is suppressed, so that a resin composition can be obtained in which particulate powder of which grain diameter is small is mixed and dispersed comparatively uniformly.
Patent Document 1: Japanese Patent Application laid open unexamined Publication No. 64-29433